Escalators and moving walks generally have balustrades that are locationally fixed at their sides. Mounted on or against the balustrades are band-shaped handrails that move relative to the balustrades as synchronously as possible with the step elements of the escalator or moving walk. The handrails consist essentially of a flexible band and can be driven by a wheel that can itself be driven directly or indirectly by a motor. At the same time, this wheel can also serve the function of a diverter sheave to divert the handrail where a change of direction of the handrail is required.
The drive of handrails should be as smooth and continuous as possible, free of jerks, as quiet as possible, and the wheel as well as the handrail itself should be constructed in such a manner that noise and wear are minimized. In particular, so-called slip-stick effects should be avoided. Slip-stick effects are instability effects associated with parameters which affect the static friction and sliding friction between the handrail and the contact surface of the wheel that drives the handrail. To realize a continuous drive of the handrail, sliding of the handrail relative to the wheel should be avoided, which means that the static friction should not fall below a certain amount. In practice, however, it is common for brief periods of sliding friction to occur, which is comparable to aquaplaning and results in the slip-stick effect.
To prevent slip-stick effects, a known wheel for driving a handrail is executed in such manner that it is formed essentially as a readily elastically deformable layer in the form of a driving-wheel tire. This driving-wheel tire is filled with a filling agent such as compressed air or an inert gas. The driving-wheel tire acts as a power transmission element in that its outer circumferential surface rests under pressure against the inner surface of the handrail so that on rotation of the driving-wheel tire the handrail is driven by the static friction acting between the power transmission element and the handrail.
Disadvantages of such driving wheel include the formation of bulges on the driving-wheel tire which occurs as a consequence of its elasticity, the substantial wear, the production of noise, and the risk of damage especially to the gas-filled driving-wheel tire.
It is accordingly an objective of the present invention to provide a wheel for driving a flexible handrail of an escalator or moving walk with which the disadvantages of the prior art are avoided.